Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $114.65   10.647%   $126.8568   $126.86   $126.85   $126.90  
  Purchase #2 $39.33   13.251%   $44.5416   $44.54   $44.55   $44.50  
  Purchase #3 $79.90   9.552%   $87.532   $87.53   $87.55   $87.50  
  Purchase #4 $199.56   8.516%   $216.5545   $216.55   $216.55   $216.60  
  Purchase #5 $33.29   6.248%   $35.37   $35.37   $35.35   $35.40  
  Purchase #6 $244.66   7.599%   $263.2517   $263.25   $263.25   $263.30  
  Purchase #7 $152.31   4.263%   $158.803   $158.80   $158.80   $158.80  
  7 purchase totals = $863.70       $932.9096   $932.90   $932.90   $933.00